JPH11264319A - Exhaust control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an exhaust amount of HC, NOx, etc., by stably obtaining self ignition combustion when performing compression self ignition combustion in a gasoline engine. SOLUTION: This type of control device has an ignition plug 22 for executing spark ignition, a first and second intake valves for opening and closing apertures 14a, 15a of a first and second intake ports 14, 15 communicated with a combustion chamber A, a first and second exhaust valves for opening and closing apertures 16a, 17a of a first and second exhaust ports 16, 17 communicated with the combustion chamber A. The second exhaust valve is opened in a specified area between the exhaust process and the intake process for partially flowing the exhaust in the second exhaust port 17 back into the combustion chamber A. Self ignition is switched selectively to spark ignition due to the ignition plug 22 according to the applied load. In such a case, an area of the second exhaust port 17 on the side of its aperture 17a is extended along the outer peripheral direction of the combustion chamber A, so as to flow the contraflow Gin of the exhaust along the outer peripheral direction of the combustion chamber A, which exhaust Gin is flowed back into the combustion chamber A by opening the second exhaust valve.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an exhaust gas control device for an internal combustion engine for introducing exhaust gas into a combustion chamber of an internal combustion engine, and more particularly, to a self-ignition operation utilizing backflow exhaust gas introduced into the combustion chamber from an exhaust port and utilizing an ignition plug. The present invention relates to an exhaust control device for an internal combustion engine that switches between spark ignition operation and engine operation in accordance with an engine load.

[0002]

2. Description of the Related Art As part of purifying exhaust gas, an internal combustion engine such as a spark ignition engine (hereinafter referred to as a gasoline engine) is used.
A technique for performing not only spark ignition operation by a spark plug but also self-ignition operation by compression has been developed and studied. According to the gasoline engine of this method, although the amount of soot and NOx generated in the exhaust gas is greatly reduced,
Since the timing of self-ignition depends on the air-fuel ratio of the air-fuel mixture, the temperature of the air-fuel mixture, and the like, it is known that it is difficult to perform self-ignition at a desired time in a wide range of load range actually used. I have.

As one method of controlling the timing of the self-ignition to expand the operation range, for example, Japanese Patent Laid-Open No. 9-28752 is disclosed.
There is a technique as disclosed in Japanese Patent Application Laid-Open No. 8 (1999) -86. This technology recirculates the exhaust gas discharged from the exhaust port to the intake port side,
The recirculated exhaust gas (external EGR gas) is introduced into the combustion chamber to control the air-fuel ratio, and the external EGR gas is cooled to control the temperature of the air-fuel mixture, thereby expanding the operating range in which good ignition can be obtained. What you want to do.

Further, as disclosed in Japanese Patent Application Laid-Open No. 5-59952, an exhaust gas recirculation passage is provided near an intake port to introduce external EGR gas into a combustion chamber, thereby controlling an air-fuel ratio in the combustion chamber. There is a technique for obtaining a good combustion state.

Further, as disclosed in JP-A-5-86992 and JP-A-9-4521, a sub-exhaust port is provided so that a part of exhaust gas flows backward into the combustion chamber, that is, reverse exhaust gas (internal EGR gas). ) Is introduced into a combustion chamber to improve combustion.

[0006]

However, the prior art as described above has the following problems. That is, in the techniques disclosed in the above-mentioned Japanese Patent Application Laid-Open Nos. 9-287528 and 5-59952, the exhaust gas discharged from the exhaust port is recirculated and introduced into the combustion chamber, or the temperature is adjusted on the way. Since it is mixed homogeneously with the fresh air and introduced into the combustion chamber, there is a problem that the responsiveness during transition when the operation mode is switched is poor, and it is difficult to control the timing of self-ignition. .

According to the techniques disclosed in Japanese Patent Application Laid-Open Nos. 5-86992 and 9-4521, exhaust gas is caused to flow backward through an exhaust port and introduced into a combustion chamber.
The distribution between the backflow exhaust gas and the air-fuel mixture cannot be controlled to a stable predetermined state, for example, a stratified state. As a result, there is a problem that it is difficult to stably obtain a desired combustion state.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to make it possible to easily control the timing of self-ignition, and to achieve a stable and favorable operation. HC, NOx
It is an object of the present invention to provide an exhaust control device for an internal combustion engine that can reduce the amount of emissions such as.

[0009]

According to a first aspect of the present invention, there is provided an exhaust gas control apparatus for an internal combustion engine, comprising two or more intake ports for opening and closing an opening of an intake port communicating with a combustion chamber. A valve, and two or more exhaust valves for opening and closing an opening of an exhaust port communicating with the combustion chamber, wherein at least one exhaust valve is opened in a predetermined region from an exhaust stroke to an intake stroke to open the exhaust port. An exhaust control apparatus for an internal combustion engine that controls a part of exhaust gas to flow back into a combustion chamber and selectively switches between self-ignition operation and spark ignition operation by a spark plug according to load to operate. Backflow directing means is provided to direct backflow exhaust flowing backward into the combustion chamber by opening at least one exhaust valve so as to flow along the outer peripheral direction of the combustion chamber.

According to a second aspect of the present invention, in the exhaust control system for an internal combustion engine according to the first aspect, the backflow exhaust directing means includes an opening-side area opened and closed by the at least one exhaust valve. The exhaust port is formed so as to extend along the outer peripheral direction of the combustion chamber.

According to a third aspect of the present invention, in the exhaust gas control apparatus for an internal combustion engine according to the first aspect, the backflow exhaust directing means is provided at an umbrella portion of the at least one exhaust valve and has a reverse flow. The configuration employs a shroud that forms a wall surface that prevents exhaust gas from flowing in directions other than the outer peripheral direction of the combustion chamber.

According to a fourth aspect of the present invention, in the exhaust control system for an internal combustion engine according to the first aspect, the backflow exhaust directing means includes an opening-side area opened and closed by the at least one exhaust valve. An exhaust port formed to extend along the outer peripheral direction of the combustion chamber and a wall surface provided at an umbrella portion of the at least one exhaust valve to prevent backflow exhaust from flowing outside the outer peripheral direction of the combustion chamber. It has a configuration that employs a shroud.

According to a fifth aspect of the present invention, in the exhaust control apparatus for an internal combustion engine according to any one of the first to fourth aspects, an exhaust cam shaft for driving the exhaust valve is provided,
In addition to the first exhaust valve cam for driving all of the exhaust valves to open during the exhaust stroke, the exhaust camshaft for driving the at least one exhaust valve also during the intake stroke for the second exhaust valve It has a configuration with a cam.

According to a sixth aspect of the present invention, in the exhaust control apparatus for an internal combustion engine according to the first to fourth aspects, an intake cam having an intake valve cam for driving the intake valve to open is formed. A shaft, and the at least one exhaust valve is driven to open by the intake valve cam even during an intake stroke.

According to a seventh aspect of the present invention, in the exhaust control system for an internal combustion engine according to any one of the first to sixth aspects, the intake port is provided at least in a predetermined direction from the opening to the combustion chamber toward the upstream side. In the region, two or more independent independent intake ports are formed, and at least one of the independent intake ports is provided with an intake passage opening / closing valve for opening and closing the passage.

According to an eighth aspect of the present invention, in the exhaust control apparatus for an internal combustion engine according to any one of the first to seventh aspects, an exhaust gas recirculation passage for recirculating exhaust gas discharged from the exhaust port to the intake port side. And a recirculation exhaust control valve that opens and closes the exhaust recirculation passage in accordance with the load and controls the flow rate of recirculation exhaust gas.

Further, as described in claim 9,
The exhaust gas control apparatus for an internal combustion engine according to claim 8, further comprising a temperature adjusting means for adjusting the temperature of the recirculated exhaust gas flowing through the exhaust gas recirculation passage.

[0018]

According to the exhaust gas control apparatus for an internal combustion engine according to the first aspect of the present invention, the backflow exhaust gas that directs the backflow exhaust gas flowing backward from the exhaust port into the combustion chamber along the outer circumferential direction of the combustion chamber. By providing the directing means, during the intake stroke, the high-temperature backflow exhaust gas flowing into the combustion chamber is mainly distributed in the outer peripheral area of the combustion chamber, and the fuel and fresh air (air) are mainly distributed in the central area of the combustion chamber. Is formed, that is, an annular stratified distribution state is formed, and in the subsequent compression stroke, compression is performed while the stratified distribution state is maintained. Then, due to the adiabatic compression action, the temperature of the backflow exhaust distributed in the outer peripheral region in the combustion chamber rises to a temperature exceeding the ignition temperature of the air-fuel mixture distributed in the central region, and the interface between the backflow exhaust and the air-fuel mixture is increased. , Compression auto-ignition combustion of the air-fuel mixture occurs.

That is, by stably forming a stratified distribution state in which the high-temperature backflow exhaust gas is distributed in the outer peripheral region of the combustion chamber, it is possible to prevent the generation of an unburned region in the dead volume region region as in the related art. Nearly complete combustion can be performed. In addition, at high load, the amount of backflow exhaust is reduced to lower the temperature of the air-fuel mixture in the compression stroke, while at low load, the amount of backflow exhaust is introduced. By increasing the temperature of the air-fuel mixture in the compression stroke by increasing the pressure, it is possible to expand the compression self-ignition combustion operation region in which the above-described good combustion can be obtained, thereby greatly reducing NOx, HC, and the like. Further, good transient response can be obtained by using the backflow exhaust from the exhaust port.

According to the exhaust gas control apparatus for an internal combustion engine according to the second aspect of the present invention, at least an opening of the exhaust port is provided as reverse flow exhaust directing means for directing the reverse exhaust gas from the exhaust port toward the outer peripheral portion of the combustion chamber. Since the side region is formed so as to extend along the outer peripheral direction of the combustion chamber, the backflow exhaust can be surely unevenly distributed in the outer peripheral region of the combustion chamber and distributed in a stratified form by a simple structure. Thereby, stable compression self-ignition combustion can be generated.

According to the exhaust gas control apparatus for an internal combustion engine according to the third aspect of the present invention, as the backflow exhaust directing means for directing the backward exhaust gas from the exhaust port toward the outer peripheral portion of the combustion chamber, the exhaust valve is provided at the head of the exhaust valve. Since the shroud provided is employed, the structure can be simplified and stable compression ignition can be achieved, and in addition, the flow rate of existing parts such as the cylinder head forming the exhaust port can be reduced, thereby reducing product cost. be able to.

According to the exhaust control apparatus for an internal combustion engine according to the fourth aspect of the present invention, at least an opening of the exhaust port serves as reverse exhaust directing means for directing the reverse exhaust from the exhaust port toward the outer periphery of the combustion chamber. Since the side region is formed along the outer peripheral direction of the combustion chamber and the shroud provided on the head of the exhaust valve is adopted,
The backflow exhaust gas can be more reliably unevenly distributed in the outer peripheral region of the combustion chamber and distributed in a stratified manner, whereby a more stable compressed auto-ignition combustion can be generated.

According to the exhaust control apparatus for an internal combustion engine according to the fifth aspect of the present invention, as a driving means for opening the exhaust valve so as to generate the backflow exhaust, a cam (for the first exhaust valve) which operates in the exhaust stroke. A dedicated cam (a second exhaust valve cam) that operates in the intake stroke is provided on an exhaust camshaft having a cam), and a configuration that is driven by this dedicated cam is adopted. No need to provide. Therefore, the backflow operation of the exhaust gas from the exhaust port into the combustion chamber can be performed at a desired timing without incurring structural complication or the like.

According to the exhaust control apparatus for an internal combustion engine according to the sixth aspect of the present invention, the driving means for opening the exhaust valve to generate the backflow exhaust is provided for driving the intake valve to open. Since the exhaust valve is driven to open using the intake valve cam of the intake camshaft, it is necessary to provide a separate camshaft etc. only by providing interlocking means from the intake cam to the exhaust valve. There is no. Therefore, the backflow operation of the exhaust gas from the exhaust port into the combustion chamber can be performed at a desired timing without failing to complicate the structure and reliably synchronizing with the intake stroke.

According to a seventh aspect of the present invention, the intake port is formed as two or more independent independent intake ports, and at least one of the independent intake ports is provided with an intake passage opening / closing valve. In the intake stroke, the intake passage opening / closing valve is closed and fresh air flows into the combustion chamber from another independent intake port, so that the fresh air flows along the outer peripheral direction of the combustion chamber. It can be swirl flow. Therefore, the backflow exhaust gas introduced from the exhaust port is distributed unevenly in the outer peripheral region of the combustion chamber under the influence of the swirl flow, thereby causing stable compression auto-ignition combustion. be able to.

According to the exhaust gas control apparatus for an internal combustion engine according to the eighth aspect of the present invention, not only the backflow exhaust gas from the exhaust port but also the recirculated exhaust gas which recirculates the exhaust gas discharged from the exhaust port to the intake port side is burned. The adoption of the configuration in which the mixture is introduced into the chamber enables the combustion temperature of the air-fuel mixture and the like to be precisely controlled, and the emission of soot, NOx, and the like can be further reduced.

According to the exhaust control apparatus for an internal combustion engine according to the ninth aspect of the present invention, not only the exhaust gas discharged from the exhaust port but also the recirculated exhaust gas which recirculates the exhaust gas discharged from the exhaust port to the intake port side is burned. In addition to the introduction into the chamber, the temperature of the recirculated exhaust gas can be adjusted, so that the combustion temperature and the like of the air-fuel mixture can be controlled more precisely, and the emissions of soot, NOx, etc. can be further increased. Can be reduced.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 and 2 are a side view and a plan view, respectively, showing a schematic configuration of an internal combustion engine (gasoline engine) provided with an embodiment of the exhaust control apparatus according to the present invention. In this gasoline engine 10, as shown in FIGS. 1 and 2, a cylindrical bore side surface 11a of a cylinder block 11 and a crown surface 12a of a piston 12 reciprocating along the bore side surface 11a.
And the lower surface 13a of the cylinder head 13
A first intake port 14 and a second intake port 15 as independent intake ports for introducing fresh air or a mixture of fresh air and fuel into the combustion chamber A are defined in the cylinder head 13. And a first exhaust port 16 and a second exhaust port 17 for discharging the exhaust gas after combustion from the combustion chamber A. Also, this cylinder head 1
3 includes a first intake valve 18 for opening and closing an opening 14a of the first intake port 14, and an opening 15a for the second intake port 15.
, A first exhaust valve 20 that opens and closes the opening 16a of the first exhaust port 16, and a second exhaust valve 21 that opens and closes the opening 17a of the second exhaust port 17. A spark plug 22 for spark ignition is attached to a substantially central portion of the lower surface 13a defining the combustion chamber A.

The first intake port 14 and the second intake port 15 are formed in substantially the same shape and at the same inclination angle so as to communicate with the combustion chamber A. An electromagnetic fuel injection valve 23 for injecting fuel is mounted in the middle, and a passage in the middle of the second intake port 15 is controlled by a drive mechanism (not shown) in accordance with the operating conditions of the engine. A swirl control valve 24 serving as an intake passage opening / closing valve for opening / closing the valve is rotatably mounted. The upstream sides of the independent first intake port 14 and the second intake port 15 are joined together to form one intake port.

The first exhaust port 16 and the second exhaust port 17 are formed such that the first exhaust port 16 has a larger inclination angle and extends obliquely upward from the combustion chamber A substantially linearly. On the other hand, the second exhaust port 17 is formed so as to extend in a substantially horizontal direction from the combustion chamber A at a small inclination angle, and a region near the opening 17a is formed in a cylindrical shape in the outer circumferential direction of the combustion chamber A. It is formed in a shape that is curved in the middle so as to extend in the tangential direction of the side surface 11a.

By forming the second exhaust port 17 as described above, when the second exhaust valve 21 for opening and closing the opening 17a is opened in the intake stroke, the exhaust remaining in the second exhaust port 17 is provided. Is directed toward the outer peripheral direction of the combustion chamber A as shown in FIG. 3, and then flows in such a manner as to be unevenly distributed in the outer peripheral region along the bore side surface 11a as shown in FIG.

That is, the second exhaust port 17 formed as described above is provided with the backflow exhaust Gin flowing back into the combustion chamber A.
Backflow exhaust directing means for directing the gas to flow along the outer peripheral direction of the combustion chamber A.

As shown in FIG. 4, a mechanism for opening and closing the first intake valve 18 and the second intake valve 19 is attached to an intake side rocker shaft 25 fixed to the cylinder head 13 so as to swing freely. First intake valve 18 and second intake valve 19
The intake side rocker arm 27 having an abutment portion 27a that abuts on the upper end of the cylinder, and is rotatably supported by the cylinder head 13 to come into contact with the intake side rocker arm 27, and the first and second intake valves 18 during the intake stroke. , 19 are constituted by an intake camshaft 29 having an intake valve cam 29a that operates to open the first exhaust valve 20 and a mechanism for opening and closing the first exhaust valve 20 and the second exhaust valve 21. An exhaust-side rocker arm 28 having a contact portion 28a that is swingably attached to an exhaust-side rocker shaft 26 fixed to the cylinder head 13 and abuts on the upper end of the first exhaust valve 20 and the second exhaust valve 21, respectively; The first and second exhaust valves 20, 21 are rotatably supported by the cylinder head 13 and open to contact the exhaust side rocker arm 28 during the exhaust stroke. Exhaust camshaft 30 provided with a second exhaust valve cam 30b to operate so as to open the second exhaust valve 21 in the cam 30a and the intake stroke for the first exhaust valve
And the like. Here, the intake valve cam 29a of the intake camshaft 29, the first exhaust valve cam 30a and the second exhaust valve cam 3 of the exhaust camshaft 30.
0b is formed so as to have a lift characteristic as shown in FIG. 5 with respect to the crank angle.

Next, the operation of the exhaust control apparatus according to this embodiment will be described.

First, when the engine is operated in the medium load range, in the exhaust stroke, the first exhaust valve 20 and the second exhaust valve 21 are both pushed down and opened by the operation of the first exhaust valve cam 30a. The burned gas in the combustion chamber A is discharged to the outside as exhaust gas through both the first exhaust port 16 and the second exhaust port 17. In the subsequent intake stroke, the first intake valve 18 is operated by the operation of the intake valve cam 29a.
And the second intake valve 19 are both pushed down to open, and the swirl control valve 24 is closed, so that the fuel injected from the fuel injection valve 23 and fresh air (air) introduced from the upstream of the intake system. The air-fuel mixture from the first suction port 14
Introduced within. In this intake stroke, at the same time as the operation of the first exhaust valve cam 30a ends, only the second exhaust valve 21 is pushed down again by the operation of the second exhaust valve cam 30b, and the second exhaust valve 21 is opened. Exhaust remaining in the exhaust port 17 flows back into the combustion chamber A.

At this time, since the second exhaust port 17 is formed such that the passage in the region on the opening 17a side extends in the outer circumferential direction of the combustion chamber A, that is, in the tangential direction of the bore side surface 11a. As shown in FIG. 6, the exhaust gas remaining inside the combustion chamber A flows backward along the bore side surface 11a, and is also affected by the swirl effect of the swirl control valve 24. The mixture Gmix is annularly unevenly distributed in the region, and forms a stratified distribution state so that the air-fuel mixture Gmix gathers in a substantially central region of the combustion chamber A.

In the subsequent compression stroke, the intake valve cam 2
9a and the operation of the second exhaust cam 30b are completed,
Then, the second intake valves 18, 19 and the second intake valve 21 are closed, and the piston 12 rises while the stratified distribution state is maintained, so that the mixture Gmix and the backflow exhaust Gin are compressed. In this compression stroke, the temperature of the backflow exhaust gas Gin distributed in the outer peripheral region in the combustion chamber A is changed to an air-fuel mixture Gm located substantially in the center of the combustion chamber A by adiabatic compression change.
ix rises to a temperature exceeding the ignition temperature of ix, and the mixture Gmix generates self-ignition combustion starting from the interface between the heated backflow exhaust Gin and the mixture Gmix. In the subsequent expansion stroke, the piston 12 is pushed down by the explosive force caused by the self-ignition combustion, and the piston 12 returns to the exhaust stroke again, and the above-described operation is repeated.

In the middle load operation range of the engine, fresh air is introduced not only from the first intake port 14 but also from the second intake port 15 with the swirl control valve 24 kept open. It is also possible to adopt.

When the engine is operated in a high load region, in the exhaust stroke, the first exhaust valve 20 and the second exhaust valve 21 are both pushed down by the operation of the first exhaust valve cam 30a to open, and combustion takes place. The burned gas in the chamber A is discharged to the outside as exhaust gas through the first exhaust port 16 and the second exhaust port 17. In the subsequent intake stroke, the operation of the first exhaust valve cam 30a ends, the first and second exhaust valves 20, 21 are closed, and the first intake valve 18 and the second intake valve 18 are activated by the operation of the intake valve cam 29a. The intake valve 19 is pushed down and opened, and the swirl control valve 24 is also opened, so that the mixture of fuel injected from the combustion injection valve 23 and fresh air (air) introduced from the upstream of the intake system is discharged. Only fresh air (air) is introduced into the combustion chamber A from the first intake port 14 and from the second intake port 15, respectively. In this intake stroke, the second exhaust valve 21 is not driven to open by the second exhaust valve cam 30b as in the case of the above-mentioned medium load region, and is in a closed state. In the closed state of the second exhaust valve 21, a known cam selection mechanism (not shown) provided on the exhaust side rocker arm 28 is operated to reduce the operating force of the second exhaust valve cam 30 b to the second exhaust valve 21. Is maintained by not transmitting to Then, the air-fuel mixture introduced in the intake stroke is uniformly distributed in the combustion chamber A.

In the subsequent compression stroke, the intake valve cam 2
After the operation of 9a is completed, the first and second intake valves 18 and 19 are closed, and the piston 12 rises to compress the air-fuel mixture while maintaining the homogenous distribution of the air-fuel mixture. Near the end, spark ignition is performed by the spark plug 22, and the air-fuel mixture produces homogeneous combustion. In the subsequent expansion stroke, the piston 12 is depressed by the explosive force caused by the spark ignition combustion, and returns to the exhaust stroke again, and the above-described operation is repeated.

In the high load operation range of the engine, the second exhaust valve 21 is kept closed during the intake stroke so that the backflow exhaust gas Gin is not introduced into the combustion chamber A. It is also possible to adopt a configuration in which a small amount of backflow exhaust is introduced by adjusting the valve opening amount of the valve 21 to cause the air-fuel mixture to perform self-ignition combustion.

When the engine is operated in the low-load region, the operation is basically the same as that in the above-mentioned medium-load operation region.
The operating force of the exhaust valve cam 30b also acts on the first exhaust valve 20, so that the first exhaust valve 20 is also opened.
Not only from the second exhaust port 17 but also from the first exhaust port 16
To increase the temperature of the air-fuel mixture in the compression stroke, thereby introducing a more stable self-recovery gas Gin into the combustion chamber A, that is, by introducing a larger amount of the back-flow exhaust gas than during the medium load operation. It is operated so that ignition combustion occurs.

By operating as described above, the operation region of stable compression auto-ignition combustion is expanded, and by introducing not the recirculated exhaust gas recirculated to the intake system but the backflow exhaust gas flowing backward from the exhaust port, Good transient response can be obtained, and there is no need to limit the amount of fresh air sucked at the time of partial load, for example, by a throttle valve provided in the middle of the intake system as in the related art. Losses are reduced, which results in improved fuel economy.

FIG. 7 shows another embodiment of the backflow exhaust directing means constituting a part of the exhaust control apparatus according to the present invention. The backflow exhaust directing means in this embodiment does not employ an exhaust port formed along the outer circumferential direction of the combustion chamber A as in the above-described embodiment, but communicates linearly with the combustion chamber A. A first exhaust port 31 and a second exhaust port 32 are employed.
In order to open and close a, a second exhaust valve 33 provided with a curved shroud 34 on an umbrella portion 33a is employed.

That is, the shroud 34 provided on the head 33a of the second exhaust valve 33 prevents the backflow exhaust gas from the second exhaust port 32 from flowing in a predetermined direction in the combustion chamber A, that is, the combustion chamber. A is formed to allow only the flow along the outer peripheral direction of A. When the second exhaust valve 34 with the shroud 34 is employed, the shroud 34 always faces a predetermined direction with respect to the combustion chamber A.
It is preferable to provide a means for preventing rotation of the second exhaust valve 33 around the axis due to reciprocation.

Incidentally, as the backflow exhaust directing means, a configuration having both the second exhaust port 17 formed along the outer peripheral direction of the combustion chamber A and the second exhaust valve 33 with the shroud 34 is employed. It is also possible.

FIG. 8 shows another embodiment of the mechanism for opening and closing the first intake valve 18 and the second intake valve 19 and the first exhaust valve 20 and the second exhaust valve 21. As shown in FIG. 8, a mechanism for opening and closing the first intake valve 18 and the second intake valve 19 is swingably attached to an intake side rocker shaft 40 fixed to the cylinder head 13 so that the first intake valve 18 And a second contact portion 42b provided on the opposite side to the first contact portion 42a and in contact with an intake camshaft 44 to be described later. The first and second intake valves 18 and 19 are rotatably supported by the cylinder head 13 and contact with the second contact portion 42b of the intake side rocker arm 42 during the intake stroke. And a mechanism for opening and closing the first exhaust valve 20 and the second exhaust valve 21. The mechanism for opening and closing the first exhaust valve 20 and the second exhaust valve 21 is a cylinder head 13. A first exhaust-side rocker arm 43 having a contact portion 43a that is swingably attached to the fixed first exhaust-side rocker shaft 41 and abuts on upper ends of the first exhaust valve 20 and the second exhaust valve 21, respectively; The first and second exhaust valves 20 and 21 are rotatably supported by the cylinder head 13 and contact the first exhaust side rocker arm 43 during the exhaust stroke.
An exhaust camshaft 45 provided with an exhaust valve cam 45a that operates to open the second exhaust valve 21 is swingably attached to a second exhaust side rocker shaft 46 fixed to the cylinder head 13. The first contact portion 47a which contacts the upper end portion (and also the upper end portion of the first exhaust valve 20 depending on the operation mode) and the opposite side of the first contact portion 47a is provided to contact the intake camshaft 44. Second contact portion 47 in contact with
and a second exhaust-side rocker arm 47 provided with b. The second exhaust side rocker arm 47 has
A known cam selection mechanism (not shown) for not transmitting the operating force of the intake valve cam 44a to the second exhaust valve 21 and for transmitting not only to the second exhaust valve 21 but also to the first exhaust valve 20. Is provided.

That is, in the exhaust stroke, the operation of the exhaust valve cam 45a of the exhaust camshaft 45 causes the first exhaust side rocker arm 43 to rotate downward (counterclockwise in FIG. 8), thereby causing the first exhaust rocker arm 43 to rotate. The exhaust valve 20 and the second exhaust valve 21 are driven to open, and during the intake stroke, the intake side rocker arm 42 rotates counterclockwise in FIG. 8 by the operation of the intake valve cam 44a of the intake camshaft 44. The first exhaust valve 18 and the second intake valve 19 are driven to open, and the second exhaust side rocker arm 47 is rotated clockwise in FIG. 8 to open only the second exhaust valve 21 (when the engine is low). In the case of load operation, the first exhaust valve 20 is also driven to open.

In this case, the first and second exhaust valves 20, 21
FIG. 9 shows the lift characteristics of the motor and the first and second intake valves 18 and 19 with respect to the crank angle. As can be understood from FIG. 9, the opening operation of the first and second intake valves 18 and 19 and the second exhaust valve 21 can be synchronized, whereby the backflow exhaust together with the air-fuel mixture can be reliably performed in the intake stroke. Can be introduced into the combustion chamber A at a predetermined timing.

FIG. 10 is a schematic diagram showing another embodiment of the exhaust control apparatus according to the present invention. In this exhaust control device, the first intake port 1 is provided similarly to the embodiment shown in FIG.
4, the second intake port 15, the first exhaust port 16, the second exhaust port 17, which is formed so that the backflow exhaust flows along the outer peripheral direction of the combustion chamber A, the fuel injection valve 23, the swirl control valve 24, and the like. In addition to the above, an exhaust gas recirculation system is provided in which exhaust gas discharged from the exhaust port is returned to the intake port side by communicating from the middle of the first exhaust port 16 (or the exhaust manifold (not shown)) to the middle of the first intake port 14. Passage 50
A recirculation exhaust control valve 51 for controlling the flow rate of the recirculation exhaust gas Gout by opening and closing the exhaust recirculation passage 50 according to the load of the engine, and a recirculation exhaust gas G flowing through the exhaust recirculation passage 50
Cooler 5 as temperature control means for controlling the temperature of out
2 and so on.

According to the above configuration, in the intake stroke, a mixture Gmix in which fresh air (air), fuel, and cooled recirculated exhaust gas Gout are mixed is introduced from the first intake port 14 into the combustion chamber A. At the same time, the backflow exhaust gas Gin is introduced from the second exhaust port 17 along the outer circumferential direction of the combustion chamber A, that is, along the bore side surface 11a.

At this time, the mixture Gmix and the backflow exhaust Gin
6, the backflow exhaust Gin is annularly distributed in the outer peripheral region of the combustion chamber A, and the air-fuel mixture Gmix including the recirculated exhaust gas Gout is distributed substantially in the center of the combustion chamber A. Will be. By forming such a stratified distribution state, stable compression auto-ignition combustion can be performed as in the above-described embodiment, and the combustion temperature of the air-fuel mixture can be more precisely controlled. And the like can be further reduced.

FIGS. 11 and 12 show an embodiment in which the exhaust control apparatus according to the present invention is applied to a direct injection gasoline engine in which fuel is directly injected into a cylinder (combustion chamber). In the direct injection engine 60, as shown in FIGS.
1a, a crown surface 62a having a concave portion 62a 'of a piston 62 reciprocating along the bore side surface 61a, and a lower surface 63a of the cylinder head 63 define a combustion chamber A,
The cylinder head 63 is provided with a first intake port 64 and a second intake port 65 as independent intake ports for introducing fresh air (air) into the combustion chamber A, and the exhausted combustion is supplied to the combustion chamber A. A first exhaust port 66 and a second exhaust port 67 for exhausting air from the exhaust port are formed. The cylinder head 63 has a first intake valve 68 for opening and closing an opening 64 a of the first intake port 64, and a second intake port 6.
5, a second intake valve 69 for opening and closing the opening 65a, and a first exhaust valve 70 for opening and closing the opening 66a of the first exhaust port 66.
A second opening / closing opening 67 a of the second exhaust port 67.
An exhaust valve 71 is reciprocally mounted, and an electromagnetic fuel injection valve 72 for directly injecting fuel into the combustion chamber A is mounted at a substantially central portion of a lower surface 63 a defining the combustion chamber A. Further, a spark plug 73 for performing spark ignition is mounted in the vicinity thereof.

The first intake port 64 and the second intake port 65 are formed so as to extend from obliquely upward to the combustion chamber A at substantially the same inclination angle. Further, the region near the opening 64a is the combustion chamber A
Is formed in a shape that is curved in the middle so as to extend in the outer circumferential direction, that is, the tangential direction of the cylindrical bore side surface 61a. A swirl control valve 74 is rotatably mounted as an intake passage opening / closing valve that is opened / closed in accordance with operating conditions to open and close the passage. The upstream sides of the independent first intake port 64 and the independent second intake port 65 are joined together to form one intake port.

By forming the first intake port 64 as described above, when the first intake valve 68 that opens and closes the opening 64a is opened during the intake stroke, it flows through the first intake port 64. The fresh air flows into the combustion chamber A as a swirl flow. By closing the swirl control valve 74 provided in the second intake port 65, the swirl flow can be made stronger. it can. still,
Even in a configuration in which the swirl control valve 74 is not provided, a desired swirl flow can be formed by employing the first intake port 64 curved as described above.

On the other hand, the first exhaust port 66 and the second exhaust port 67 are connected to the first exhaust port 66 similarly to the above-described embodiment.
Is formed so as to extend substantially straight obliquely upward from the combustion chamber A at a larger inclination angle, and the second exhaust port 67 is formed at a small inclination angle in a substantially horizontal direction from the combustion chamber A. The bore 67 extends in the direction of the outer periphery of the combustion chamber A, that is, in a cylindrical shape.
It is formed in a shape in which the middle is curved so as to extend in the tangential direction of a.

By forming the second exhaust port 17 as described above, when the second exhaust valve 21 that opens and closes the opening 67a is opened in the intake stroke, the exhaust remaining in the second exhaust port 17 is opened. Are directed and directed toward the outer peripheral direction of the combustion chamber A as shown in FIG. 3, and further flow along the outer peripheral portion under the influence of the swirl flow of the fresh air, Thereafter, as shown in FIG. 2 described above, the distribution is unevenly distributed in the outer peripheral region along the bore side surface 61a. That is, the second exhaust port 67 formed as described above constitutes a backflow exhaust directing unit that directs the backflow exhaust Gin flowing backward into the combustion chamber A so as to flow in the outer peripheral direction of the combustion chamber A. I have. In this embodiment, the mechanism for opening and closing the first and second intake valves 68 and 69 and the first and second exhaust valves 70 and 71 and the operation of the entire apparatus are the same as those in the previous embodiment. Therefore, the description is omitted here.

In the embodiment described above, the second exhaust valve cam 30b that opens and closes the second exhaust valves 21 and 71 (and, in some cases, the first exhaust valves 20 and 70) is used to operate the entire engine. Although a cam profile with a constant cam profile (constant cam height) is applied in the region, for example, as shown in FIG. 13, even if a variable mechanism that selectively uses, for example, three types of cam profiles according to the operating region of the engine is adopted. Good. That is, in the low load operation region, the exhaust valve cam having the largest valve lift amount is selected, and in the high load operation region, the exhaust valve cam having the smallest valve lift amount is selected. In the operating region, a structure may be adopted in which an exhaust valve cam that can obtain a substantially intermediate valve lift amount is selected.

According to this configuration, in the high-load operation region of the engine, as shown in FIG. 14, a stratified distribution state is formed in which the amount of the backflow exhaust Gin is smaller than the amount of the air-fuel mixture Gmix. In the low load operation region of FIG.
As shown in (1), a stratified distribution state in which the amount of the backflow exhaust Gin is increased as compared with the amount of the air-fuel mixture Gmix is formed. As a result, stable compression self-ignition combustion can be performed, and the amount of emissions of soot, HC, NOx, and the like can be significantly reduced.

In the embodiment described above, the first
As the intake valve cam 29a for opening and closing the intake valves 18, 68 and the second intake valves 19, 69, a cam profile having a constant cam profile (constant cam height) in the entire operation range of the engine is used. As shown in FIG. 16, for example, a variable mechanism that selectively uses, for example, three types of cam profiles according to the operating region of the engine may be employed. That is, in the low load operation region, the intake valve cam that minimizes the valve lift is selected, and in the high load operation region, the intake valve cam that maximizes the valve lift is selected. In the region, a structure may be adopted in which an intake valve cam is selected so that a substantially intermediate valve lift can be obtained.

According to this configuration, in the high load operation region of the engine, the inflow of the mixture Gmix increases,
The amount of the backflow exhaust Gin is relatively reduced as compared with the amount of the mixture Gmix, and a stratified distribution state as shown in FIG. 14 is formed. On the other hand, in the low-load operation region of the engine, the amount of the mixture Gmix inflows Decreases, the amount of the backflow exhaust Gin relatively increases as compared with the amount of the air-fuel mixture Gmix, and a stratified distribution state as shown in FIG. 15 is formed. As a result, the compressed self-ignition combustion can be performed in a stable manner as described above, and the amount of emissions of soot, HC, NOx, and the like can be significantly reduced.

In the above-described embodiment, only one cylinder of the engine has been described. However, it is needless to say that the present invention can be applied to a multi-cylinder engine.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a part of a gasoline engine provided with an exhaust control device according to the present invention.

FIG. 2 is a plan view showing a part of a gasoline engine provided with the exhaust control device according to the present invention.

FIG. 3 is a plan view for explaining a flow of backflow exhaust flowing backward from an exhaust port constituting the exhaust control device according to the present invention.

4A and 4B show a mechanism for opening and closing an intake valve and an exhaust valve of an internal combustion engine. FIG. 4A is a longitudinal sectional view, and FIG. 4B is a plan view of an intake camshaft and an exhaust camshaft.

FIG. 5 is a diagram showing valve lift characteristics of an intake valve and an exhaust valve with respect to a crank angle.

FIG. 6 is a diagram showing a distribution state of a backflow exhaust gas and an air-fuel mixture in a combustion chamber.

7A and 7B show another embodiment of the backflow exhaust directing means constituting the exhaust control apparatus according to the present invention, wherein FIG. 7A is a plan view and FIG. 7B is a side view of an exhaust valve.

8A and 8B show another embodiment of a mechanism for opening and closing an intake valve and an exhaust valve of an internal combustion engine, wherein FIG. 8A is a longitudinal sectional view, and FIG. 8B is a view of an intake camshaft and an exhaust camshaft. It is a top view.

FIG. 9 is a diagram showing valve lift characteristics of an intake valve and an exhaust valve with respect to a crank angle.

FIG. 10 is a plan view showing another embodiment of the exhaust control device according to the present invention.

FIG. 11 is a longitudinal sectional view showing a part of a direct injection gasoline engine provided with the exhaust control device according to the present invention.

FIG. 12 is a plan view showing a part of a direct-injection gasoline engine provided with the exhaust control device according to the present invention.

FIG. 13 is a diagram showing valve lift characteristics with respect to crank angle when a configuration is adopted in which three types of cams having different cam heights are selected as exhaust valve cams in accordance with operating conditions of an engine.

FIG. 14 is a diagram showing a distribution state of a backflow exhaust gas and an air-fuel mixture in a high load operation region.

FIG. 15 is a diagram showing a distribution state of a backflow exhaust gas and an air-fuel mixture in a low load operation region.

FIG. 16 is a diagram showing a valve lift characteristic with respect to a crank angle in a case where a cam having three kinds of cam heights is selected as an intake valve cam in accordance with an operating condition of an engine.

[Explanation of symbols]

 Reference Signs List 10 gasoline engine 11 cylinder block 11a bore side surface 12 piston 12a crown surface 13 cylinder head 13a bottom surface 14 first intake port 14a opening 15 second intake port 15a opening 16 first exhaust port 16a opening 17 second exhaust port 17a opening Part 18 First intake valve 19 Second intake valve 20 First exhaust valve 21 Second exhaust valve 22 Spark plug 23 Fuel injection valve 24 Swirl control valve (intake passage opening / closing valve) 25 Intake side rocker shaft 26 Exhaust side rocker shaft 27 Intake Side rocker arm 28 exhaust side rocker arm 29 intake camshaft 29a intake valve cam 30 exhaust camshaft 30a first exhaust valve cam 30b second exhaust valve cam 31 first exhaust port 32 second exhaust port 33 second exhaust valve 33a Umbrella part 34 Shroud 4 Intake side rocker shaft 41 First exhaust side rocker shaft 42 Intake side rocker arm 43 First exhaust side rocker arm 44 Intake camshaft 44a Intake valve cam 45 Exhaust camshaft 45a Exhaust valve cam 46 Second exhaust side rocker shaft 47th 2 Exhaust side rocker arm 50 Exhaust recirculation passage 51 Recirculation exhaust control valve 52 Cooler (temperature adjusting means) 60 Direct injection gasoline engine 61 Cylinder block 61a Bore side surface 62 Piston 62a Crown surface 62a 'Recess 63 Cylinder head 64 First intake port 65 First 2 intake port 66 first exhaust port 67 second exhaust port 68 first intake valve 69 second intake valve 70 first exhaust valve 71 second exhaust valve 72 fuel injection valve 73 spark plug 74 swirl control valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 21/08 301 F02D 21/08 301Z 41/02 301 41/02 301E 351 351 43/00 301 43/00 301B 301N 301Z F02M 25 / 07 510 F02M 25/07 510B (72) Inventor Toru Noda 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Nissan Motor Co., Ltd.

Claims (9)

[Claims] At least two intake valves for opening and closing an opening of an intake port communicating with a combustion chamber, and at least two exhaust valves for opening and closing an opening of an exhaust port communicating with a combustion chamber are provided. One exhaust valve is opened in a predetermined region from the exhaust stroke to the intake stroke to control a part of the exhaust gas in the exhaust port to flow back into the combustion chamber, and the self-ignition operation and the ignition plug are performed according to the load. An exhaust control apparatus for an internal combustion engine that operates by selectively switching between spark ignition operation and spark ignition operation, wherein backflow exhaust gas that flows back into the combustion chamber by opening at least one exhaust valve flows in the outer peripheral direction of the combustion chamber. An exhaust control device for an internal combustion engine, comprising: a backflow exhaust directing means for directing the exhaust gas in such a manner. 2. The exhaust gas directing means according to claim 1, wherein the backflow exhaust directing means is an exhaust port formed such that an opening side region opened and closed by the at least one exhaust valve extends along an outer peripheral direction of a combustion chamber. The exhaust control device for an internal combustion engine according to claim 1. 3. The backflow exhaust directing means is a shroud provided on an umbrella portion of the at least one exhaust valve and forming a wall surface that prevents backflow exhaust from flowing in a direction other than the outer peripheral direction of the combustion chamber. The exhaust control device for an internal combustion engine according to claim 1, wherein: 4. An exhaust port, wherein said backflow exhaust directing means is formed so as to extend an opening side region opened and closed by said at least one exhaust valve along an outer peripheral direction of a combustion chamber, and said at least one exhaust valve. 2. The exhaust control system for an internal combustion engine according to claim 1, wherein the shroud is provided at the head of the engine and forms a wall surface for preventing backflow exhaust from flowing in a direction other than the outer peripheral direction of the combustion chamber. 5. An exhaust camshaft for driving said exhaust valve, said exhaust camshaft driving a first exhaust valve cam for opening all of said exhaust valves in an exhaust stroke, and said at least one exhaust camshaft. The exhaust control device for an internal combustion engine according to any one of claims 1 to 4, further comprising a second exhaust valve cam that drives the two exhaust valves to open during the intake stroke. 6. An intake camshaft on which an intake valve cam for driving the intake valve to open is formed. The at least one exhaust valve is opened by the intake valve cam even during an intake stroke. The exhaust control device for an internal combustion engine according to any one of claims 1 to 4, which is driven. 7. The intake port is formed as two or more independent independent intake ports in at least a predetermined region going upstream from an opening to a combustion chamber,
The exhaust control device for an internal combustion engine according to any one of claims 1 to 6, wherein at least one of the independent intake ports has an intake passage opening / closing valve for opening / closing a passage thereof. 8. An exhaust gas recirculation passage that recirculates exhaust gas discharged from the exhaust port to the intake port side, and a recirculation exhaust gas control valve that opens and closes the exhaust gas recirculation passage according to a load to control a flow rate of recirculated exhaust gas. 2. The method according to claim 1, wherein
8. The exhaust control apparatus for an internal combustion engine according to any one of claims 7 to 7. 9. The exhaust control apparatus for an internal combustion engine according to claim 8, further comprising a temperature adjusting means for adjusting the temperature of the recirculated exhaust gas flowing through the exhaust gas recirculation passage.